When growing marijuana indoors, light energy has the largest impact on yield and performance. It is the main energy driving photosynthesis in an indoor garden.
This is why it is so important for indoor growers to not only purchase effective lighting systems, but to also maintain the light output of those systems.
Regularly changing the bulbs and cleaning away dust and debris are two easy ways a cannabis grower can keep the light energy in the garden powerful and uniform.
With a well-maintained lighting system, a grower can begin to implement other techniques to better utilize the given light energy and to maximize his or her return on investment.
In every indoor garden, there is a “sweet spot” of light energy. Finding the sweet spot and having the majority of the plant canopy in this area are keys to maximizing a grow room's efficiency.
The Sweet Spot for a Horticultural Lighting System
The sweet spot refers to the area just below the lighting system, where the usable light energy is the most intense. For most indoor gardens, this area is located eight to 20 inches below the horticultural lighting system.
The location of the sweet spot can vary from grow room to grow room, but will revolve around two important factors: the wattage, or energy intensity, of the light source and how the excess radiant heat is removed.
For example, a grower can place plants closer to a 400W light source than a 1,000W light source. Also, a light source that is air-cooled to remove the radiant heat can be placed much closer to the plants than a light source that is not air-cooled.
For many growers, a bit of experimentation will be necessary to find the garden’s light energy sweet spot. Plants placed too close to the light source can show signs of bleaching or burning, while plants placed too far away will become leggy or wispy.
Manipulating the plants themselves or the way the plants grow is a great way for marijuana growers to increase the amount of plant material that lies within the light energy sweet spot.
The most common plant manipulation methods used by indoor cannabis cultivators are staking, trellising, pruning, topping, and super cropping.
The first two methods, staking and trellising, are techniques used to better support or train the plants to most efficiently utilize the light energy.
The other three methods, pruning, topping, and super cropping, are techniques that alter plant growth directly.
Plant manipulation methods can be used in conjunction with one another or on their own to help a grower increase his or her yields by using the given light energy more efficiently.
Plant Manipulation Ideas
Staking is one of the most common methods marijuana growers use to manipulate or support the plants to increase efficiency.
During vegetative growth, stakes can be used to pull plants apart, resulting in better light penetration and fuller, bushier growth. During the blooming stage, stakes can be used to support heavy fruit or flowers that would otherwise sag out of the lighting system’s sweet spot.
Trellis netting is an invaluable tool for the indoor grower and my personal favorite for plant manipulation. Trellis netting can be stretched horizontally just below the light system’s sweet spot to assist a grower in spreading, supporting, and controlling the height of the plants.
Trellis netting used in this way will maximize the available light energy and increase the garden’s overall efficiency. Trellis netting can also be used as a vertical support system.
Many growers will prune some of the larger shade leaves to improve light penetration to the lower flower sets. Another common pruning technique is to remove all the lower section leaves that are positioned below the sweet spot.
This allows the plant to direct its energy toward developing the flowers within the sweet spot. This method is especially effective when combined with a horizontal trellis.
Topping is a technique where the tops of the plant are pruned or removed. This is generally done at a node space (the place where horizontal branching occurs). At each node space, there are two potential new shoots.
The idea behind topping is for every top removed, two new shoots take its place, thereby increasing the number of shoots, and eventually fruit or flowers, that will develop.
Growers who use the topping technique can better control the vertical growth of the plant and position more vegetation in the lighting system’s sweet spot.
Super cropping is similar to topping because the purpose is to get the plant to grow new shoots from the node spaces. However, with super cropping, the tops are not cut or removed, but are bent to the point of damaging them.
The best way to implement this is to squeeze the stem between the thumb and pointer finger until the stem folds like a drinking straw. The advantage of super cropping is that the tops are retained while still promoting new shoots from the node spaces.
As with topping, plants that are super cropped will become extremely bushy and will have more vegetation that can be placed in the sweet spot of the lighting system.
Regardless of which plant manipulation technique a grower decides to implement, the end goal is the same: to best utilize the given light energy and maximize the garden’s yield.
Every indoor garden has a limited amount of available light energy and to make an indoor marijuana garden as effective and efficient as possible, a grower must make the most of the garden’s given light energy.
Although ventilation and nutrition also play key roles in an indoor garden’s performance, the light energy is most vital to the success or failure of the garden.
Marijuana growers who implement plant manipulation techniques to best utilize the given light energy will yield a higher ratio of weight to watts consumed at harvest time.
Put another way, implementing plant manipulation techniques increases efficiency in the garden that always equates to a higher return on investment for the grower.